Hearing restoration or compensation devices, commonly known as hearing aids, provide a tremendous benefit to a patient with congenital hearing loss or whose hearing has deteriorated due to age, genetics, illness, or injury. There is a wide variety of commercially available devices that can be worn externally or can be implanted within the body of the patient.
In general, it is desirable to provide a high level of gain in the device, so that ambient sound may be significantly amplified for the patient. However, if the gain is too high, some sound may leak from the output speaker to the input microphone, and the device may produce acoustic feedback. Acoustic feedback is a highly undesirable condition, and can lead to a loud squealing noise heard by the patient.
Accordingly, there exists a need for a diagnostic tool that can characterize the performance of the device, so that the gain may be set at a level below the threshold at which acoustic feedback occurs. In addition, for implantable devices, the characterization may be repeated over an extended period of time, and may help diagnose tissue growth or fluid in the middle ear.